1. Field of Invention
This invention relates to mixed metal oxides with the perovskite structure and their use as catalysts. More particularly, this invention relates to the use of perovskites as catalysts for the conversion of synthesis gas (syn gas).
2. Prior Art
The conversion of syn gas, which is comprised primarily of carbon monoxide and hydrogen, to various carbon containing compounds is well known. A variety of catalysts, including particularly the group 8 and group 1B and 2B metals have been employed in the conversion of syn gas. Most of these catalysts have mainly resulted in the formation of broad, complex mixtures of hydrocarbons and oxygenated organic compounds and carbon dioxide. Hydrocarbon formation, particularly methane formation, is thermodynamically favored over the formation of oxygenated organic compounds. In addition, the formation of carbon dioxide and hydrogen is also favored over the formation of oxygenated organic compounds, particularly those containing two or more carbon atoms. Therefore, in the conversion of syn gas to useful organic products, there is a need for catalysts that selectively produce lower oxygenated organic compounds, particularly those containing one to six carbon atoms from syn gas.
In U.S. Pat. No. 4,312,955, lanthanum rhodate perovskites are used as catalysts for the highly selective conversion of syn gas to methanol. Some of the perovskites produce other oxygenated compounds, such as ethanol and propanol. However, non-lanthanum rhodate catalysts are not disclosed.
In "The Formation of Oxygen-containing Organic Molecules by the Hydrogenation of Carbon Monoxide using a Lanthanum Rhodate Catalyst," by Watson and Somorjai, Journal of Catalysis 74, 282-295, 1982, syn gas conversion employing LaRhO.sub.3 at a reaction temperature of 225.degree. C.-375.degree. C. and at a pressure of 1 to 10 atmospheres is disclosed. At lower temperatures, the major product observed is methanol, but at 300.degree. C. the major products are acetaldehyde and ethanol. The combined selectivity of this catalyst for acetaldehyde and ethanol is reported to be 45-49 percent. However, other perovskite catalysts are not disclosed.
In U.S. Pat. No. 4,126,580 a variety of perovskite catalysts is disclosed. According to the patent, the perovskite catalysts, and particularly those containing Fe, Co, Ni or Ru, can be utilized in the reduction of carbon monoxide with hydrogen at temperatures ranging from 150.degree. C.-600.degree. C. and pressures up to 15,000 psi to produce hydrocarbons with or without the concomitant formation of alcohols, aldehydes, ketones or fatty acids. However, there is no disclosure that any of the catalysts can selectively produce oxygenated compounds.
U.S. Pat. No. 2,517,035 discloses the use of La.sub.2 O.sub.3 as a promoter for cobalt and iron catalysts in syn gas conversion. According to the patent, the preferred catalyst is a mixture of Co.sub.3 O.sub.4, diatomaceous earth, and magnesium oxide. However, no disclosure is made of the catalytic activity of perovskites.
It is an object of this invention to provide a means for producing lower oxygenated organic compounds from synthesis gas.
It is a further object of this invention to provide a means for selectively producing lower oxygenated organic compounds from synthesis gas utilizing perovskite catalysts.
It is also an object of this invention to form high yields of lower oxygenated organic compounds, particularly those containing one to six carbon atoms from synthesis gas.
These and other objects are obtained by the process or products of the present invention.